Hob grinder



H. PELPHREY Oct. 8, 1946.

HOB GRINDER Filed NOV. 26, 1943 '7 Sheets-Sheet 1 INVENTOR H-rrrg 8, 1946n l H. PELPHREY Oct Hoa GRINDER Filed Nov. 2e, 1943 '7 Sheets-Sheet 2 R w. N m v N RVv 1 rl A Q l.. QMN. E a gm ad f/ .o l l 1| r NNN E M\ p Il l) Y Il I B Nwv\ .l l -l v .WN QW. Q\ QN NWN wm 6 W Q MN SW w MU, www bv% 06k.. 8,A 1946e H, PELPHREY 2,408,949

HOB GRINDER Filed Nov. 26, 1943 7 Sheets-Sheet 4 I N VEN TOR; fZ/rey.

HL PELPHREY @ci s, w46.

HOE GRI-NBER Filed Nov. 26, 1943 '7 Sheets-I-Sheet 5 INVENTOR I y M ATTORNEYS' H. PELPHREY Oct., 8, 1946c Ho GRINDER Filed Nov. 26, 1945 'I sheets-sheet 6 Oct. 8, e1946. H. PELPHREY 2,408,949

HOB GRINDER l Filed Nov. 2e', i943 'I sheets-sheet 7 Patented Oct. 8, 1946 HOB GRINDER Harry Pelphrey, Detroit,

gan Tool Company, tion of Delaware Mich., assignor to Michi- Detroit, Mich., a corpora- Application November 26, 1943, Serial No. 511,788

9 Claims.

The present invention relates to a machine for producing cutting tools and particularly relates to a machine for grinding side relief on the teeth of hobs ofthe enveloping type, that is, hobs designed for use in cutting the worm wheel or worm gears of' gear sets embodying the I-lindley or globoidal principle.

In particular, the machine of the present invention is an improvement over the side relief grinding embodiment disclosed in Scott Patent No. 1,980,444.

In providing the side relief, the sides of the hob teeth are relieved from the front cutting edges away from the normal lead of the thread or tooth side in order to relieve the side from contact with the flanks on the worm wheel to be cut. The tool, or grinding element, is located at a normal position at the cutting edge of the teeth, and as the hob and main tool carriage are rotated in normal synchronism a relative rotative movement, with respect to the main tool carriage, is imparted to the tool to retract the tool with respect to its normal position as it engages the sides of each tooth. The tool returns to its normal position at the cutting edge of each tooth.

The primary object of the present invention is to provide an improved means for imparting the retraction to the tool from its normal lead so that there is a uniform, synchronous drive between the hob spindle and the mass of the main tool carriage. A further object of the present invention is to provide an improved means of the type mentioned which is independent of the main drive between the hob spindle and the mass of the main tool carriage so that there is no shockload on the drive worm during the shifting of the tool from its normal lead.

A further object of the invention is to provide an improved machine of the type mentioned by which the side relief may be accurately imparted to the sides of the hob teeth and in which the machine will maintain its accuracy over a long life.

Other objects of the invention will become apparent from the following specification, the drawings relating thereto and from the claims hereinafter set forth..

In the drawings in which like numerals are used to designate like parts in the several views throughout:

Figure l is a perspective View taken from the front right side of a machine embodying features of the present invention;

Fig. 2 is a view similar to Fig. l taken from the left front side of the machine;

Fig. 3 is a vertical cross-sectional view through the lcenter of the tool carrying table and the main table, and showing the mechanism for imparting the retraction of the tool from its normal lead;

Fig. 4 is a cross-sectional and elevational view taken substantially along the lines 4-4 of Fig. 3;

Fig. 5 is a fragmentary cross-sectional view taken substantially along the lines 5-5 of Fig. 3;

Fig. 6 is a cross-sectional View illustrating the ratchet means for driving the retracting cam in one direction;

Fig. 7 is a cross-sectional view taken substantially along the lines 1-1 of Fig. 6;

Fig. 8 is a diagrammatic view of means for the machine of Fig. 9 is a perspective View of a to be worked upon by the machine of invention;

Fig. 10 is an enlarged partial view of the structure shown in Fig. l.

the driving hob of the type the present Referring to Fig. 9 a hob of the type disclosed' in Cone Patent 2,026,215 is illustrated and is generally indicated at Il). As shown, the hob teeth are formed from a thread having a normal lead, and in the embodiment illustrated there are a plurality of such threads. Several of the teeth of one thread are indicated at II, I2, I3, and I4; and several of the teeth of an adjacent thread are indicated'at I4, I5, I6, I1, and I8. Each of the teeth is provided with a cutting edge, 20, and it will be understood that such cutting edge 20 is located in the position described in the above mentioned Cone patent. The side relief is provided on the sides of each of these teeth indicated at 22, and it is the provision of this side relief to which the present invention is directed.

Referring to Figs. l through 8, an embodiment of the present invention is illustrated by which the side relief above mentioned is provided. The machine is automatically controlled and comprises a base 24, which serves spindle having a main, rotatable work table 26 fixed thereto for rotation there 'th. The forming means, in the form of a grinder, is generally indicated Vat 28 and is mounted on an auxiliary table 30 for rotation therewith. The table 30 is mounted on table 26 and is moved relative thereto to impart the retractive movement above mentioned, which will be described in greater detail hereinafter.

The hob I0, to be relieved, is mounted to a horizontal slide 29, which is mounted on horizontal, parallel ways 3|, formed on the top surface of the base 24, so that such slide 29 is slidthe present invention;

able on parallel lines toward and away from the table 26 and in a direction normal to the axis of table 26. The slide 29 serves to mount a head stock 32 and an adjustable tail stock 34 so that the hob Hl may ybe removably mounted therein with its axis horizontal and at a right angle to the direction of movement of the slide 29.

The head stock 32 and tail stock 34 are mounted on a vertically adjustable slide 33 which is mounted on parallel ways formed on the front 29 so that the vertical posioperatively connecting the hand wheel and crank to their slides will be apparent to those skilled in the art.

In the forming means generally indicated at 28, the tool employed to impart the side relief comprises a small, cylindrical pencil grinding element 36 which is secured to a spindle 38 and rotatably mounted in bearing blocks 40. bearing blocks 40 are adjustably mounted in a guideways on the under side of block 44 and which are substantially parallel to the axis of the grinding element 36 so that block 44 may be adjustably fixed. on block 46. The block 46 is blocks gage pulley 52, the motor 56 is mounted on an overhanging platform 58. The platform 58 is mounted on a vertical pivot about the outer end of an arm 60 and the inner end of arm 68 is pivotally connected, through a vertical pivot pin to the outer end of another arm 62. The arm on the base 24 54 with the pivotal` movement of the spindle 38 is obtained. The pivot pins between the arms and the platform 58 are preferably mounted in ball bearing so as to provide for ease in movement.

It will be appreciated that the head stock spindle, carrying the hob l0, is disposed on an axis perpendicular to theaxis of rotation of the main table 26 and that the hob is driven in synchronisrn with the main table. The drive for the table and. the hob is reversible so that the pencil grinder 36 passes along one side of the teeth of one of the threads of the hob from one end thereof to the other and the drive is then reversed to return the grinding element 36 back to its original position between adjacent threads. When moving in one, or the first, direction, the grinding wheel engages the cutting edge 20 of each of the hob teeth. Since the sides 22 are relieved from the cutting edge 20 to the back edge of each of the teeth, and since such relief is gradual, it will be appreciated that the grinding grinding element follows a staggered path.

Such variation in relative movement of the grinding element with respect to the hob teeth relative movement is imparted to table 30 independently of the drive between table 26 and the hob so that the shock load of providing the retraction and return to normal lead is taken off the main drive. The main drive is uniform for the mass of the main tool carriage and the retraction is `imparted to a relatively small mass made up of the auxiliary table 30 and the forming means 23.

cylindrical member 66. is mounted and xed thereto and may be considered as an integral part thereof. An annular top plate 68 having a central opening 16 therethrough is mounted to the top of member 66 and iixed thereto. The main table 26 has a depending, integral hollow shaft portion 12 which lpasses through opening 10 with the table 26 supported on the top surface of member 68. A pair of cooperating bearing rings 14 and 76 are xed to the top surface of member 68 and the under surface of table 26, respectively, to provide a bearing for the` relative rotation of table 26 with respect to member 68. A ring member 18 embraces the bearings 14 and 16 and is received Within the annular shoulders provided in members 68 and 26 to provide for axial alignment of the table 26. A ball bearing assembly race of bearing as- |29. For rotation of the main Ztable 26,

mounted with respect thereto by means of a ball bearing assembly 90 which is mounted within annular ball bearing mounting members 92 and 94. The member 92 is fixed to member 86 by means of is fixed to member 92 by means of screws 98 so that the member 94 is stationary with respect to the base.

The table 38 is mounted on table 25 for movement therewith and for relative rotative movement with respect thereto. An annular bearing ring |52 is fixed to the top surface of table 28 and engages the under surface of table 30. The outer edge of ring |02 overhangs the edge of table 28; and a bearing ring |04 having an inwardly directed annular shoulder |05 is fixed to table 30 so that the top surface under surface is Xed upwardly within an axial opening H in table 30. A thrust bearing assembly ||2 is disposed between member |08 and opening Hi) with the outer race thereof bearing against a shoulder provided in opening i i9 and with the inner race thereof held in place by an overhanging plate member ||4 fixed to the top surface of |88. A cover plate H may be removedly fixed to table 30 over opening H0 and flush with the surface thereof.

The relative movement between tables 28 and 30, or the retraction of grinding element 98 from its normal lead, is imparted through the drive connection between tables 2S and 89. Such drive connection includes a plate member which is fixed to the under surface of table 30 within a recess |22. A pair of depending members |24 is fixed to the plate member and each of the members |24 is formed with a sloping cam edge |25, such cam edges |28 being disposed to face inwardly and toward each other. A rod member |28 is disposed within a cylindrical, radial opening |30 provided in table 25 and projects outa space 13| in table 26 with' which the members |24 extend. The space I3| is of such extent as to permit limited movement of members |24 therein. Y

A bearing sleeve |34 opening |30 and slidably receives therein the rod mem er |28. The outer end of member |28 is formed with tapering flats or cam edges |36 which are adapted to bear against in one direction, a spring |38 is disposed in an opening |40 provided in table 28 and may be adjustably held therein by means of a screw plug |42. The inner end of spring |38 bears against the adjacent face of one of the members |24 and resiliently urges it into engagement with the adjacent cam edge similar to |40 is provided in the opposite side of so that when the machine is reversibly operated the spring |38 is placed in the opposite posite member |24 and the opposite edge |36.

The inner end of member |28 is formed with a sloping flat |44 which is adapted to bear against a complementary, sloping flat |46 formed on the top portion of a rotatable cam pad |48. The depad |48 is rotatably reopening formed in the top end of an actuator rod |50. The actuator rod |50 is received through the axial opening in shaft portion 12 and a bearing sleeve |52 is disposed between the upper end of member |50 and shaft portion 12. Such member |52 is received within an enlarged portion vof the axial opening. The lower end of member |50 is keyed to member 94 by means of key |54 so that the member |50 is rotatably stationary with respect to table 2B but may be vertically moved with respect thereto. Y

The lower end of member |50 has a tapped axial opening formed therein which receives a screw |58 having a depending cam follower |58 formed on the end thereof. The screw |55 may be adjusted to adjust the follower |58 and may be held in position by means The cam |58 is adapted to engage the periphery of a rotatable cam keyed to shaft |515. lt will be appreciated that as the shaft |84 is turned in the direction of the arrow in Fig. 4, the cam follower |50 to move upwardly. tables 26 and 80 in One member |50 moves upwardly surface |46 slides along surface IM and moves member |28 radially outwardly. |48 rotates with the tables. As member |28 moves outwardly, surface |38 slides outwardly against surface |28, in the relationship shown in Fig. 5, thereby causing a relative retraction of table 30 with respect to table 26. This causes a corresponding relative retraction of the grinding element 35. The surface of cam |52 is such that there is one complete revolution of cam |82 for each tooth and the retraction is gradual to provide the gradual relief and the grinding element is returned to its normal position for the next tooth.

As mentioned above, the spindle to which table 25 is attached is driven by gear wheel 84. Re-

ferring to Fig. 8, the drive for the ma'n table,

, the hob and also the shaft |54, which rotates cam and worm |82, is diagrammatically illustrated. The hob |0 is mounted to the head stock having a hob driving spindle |88 mounted therein. The hob spindle and the gear 84 are driven in uniform synchronism at all times. The hob spindle |80 is connected to a drive shaft |82 through a worm gear |84 and a worm |86. The worm gear |84 |85 are of the double enveloping type disclosed in Cone Patent No. 1,822,800. Shaft |82 has a warm gear |88 keyed thereto which meshes with a worm |99. I'ilhis worm and gear set is also of the Cone type. Worm |90 is keyed to shaft |92 which also has gear |94 keyed thereon. Gear |94 meshes with gear |99 which is keyed to shaft |98. Shaft |98 is operably connected through a conventional clutch 200 with a drive pulley 202. The drive pulley 202 is driven by a suitable belt i or chain 204 which is trained about a motor pulley 285 keyed to the outer end of motor shaft 208 of main drive motor 2|0. The main drive motor 2 |9 is a variable speed reversible motor. It will thus be the hob spindle |80 is driven by the motor 2 |0 through the chain of shafts and gears just described.

The gear 84 is synchronously driven with the liob spindle |80. To accomplish this, shaft |82 is connected to shaft 2|2 through change gears and 220. Shaft 2|2 is drivingly connected to shaft 222 through a matching differential, generally indicated at 224. Such matching differential may be of the same structure as the matching differential employed in the machine of Pelphrey application Serial No. 435,649, filed March 2l, 1942. The matching differential 224 is employed for the purpose of providing relative side feed of the grinding element 38, which is driven by gear 84, with respect to the hob so that the grinding element-l may be properly set for its initial engagement with the grinding edges.

The matching differential 224 includes a housing or and may be revolved about the axis of shafts 2|2 and 222. A gear 228 is keyed to the inner end of shaft 22 and another gear 238 axis but revolves about the axis of gears housing 226 is revolved. have the same ,outside has less teeth than gear 30. For example, gear 2,30 may have 24 teeth,

13tooth gear.

volute curve are tion of these gear teeth. By rotating housing gears 244, shaft 248 and 250, shaft 252, bevel gears hand crank is keyed.

The drive shaft 222 thereto which meshes 246, gears has a worm 258 keyed with the gear 84.

4 gear 84 and worm 258 are a set of the Cone type mentioned above.

By driving `the clockwise rotation only of |64 is driven through a `bevel gear set 264 by shaft 266. The shaft 265 is driven by shaft 268 throng-h a one-way drive or ratchet 'mechanism in Figs. 6 and 7. It comprises a mounting frame 2 within which the bevel gear 264 and shafts 254, and shaft 256, to which the i266 and 268 are mounted.

to the first cutting edge t0 be engaged. The cam may be adjusted to its starting position by adjusting the index platel 216 with respect to member 288. When the motor is 0 tates in the direction of arrow What is claimed is: l. Apparatus for side-relieving the teeth o1' hobs comprising, in combination, a rotatable hob l for effecting the relief on the teeth, said iasttion of travel only and dependent upon the numnamed means including means providing the drivber of teeth to be relieved between the ends of the ing connection between said tables. thread for effecting the relief on said teeth. f

2. Apparatus for side-relieving the teeth of 5. Apparatus for side-relieving the teeth of hobs comprising, in combination, a rotatable hob hobs comprising, in combination, a rotatable hob support, a rotatable, main table adapted to rotate support, a rotatable, main table adapted to roabout an axis perpendicular to the axis of rotatate about an axis perpendicular to the axis of tion of said hob support, driving means for rorotation of said hob support, reversible driving tating said hob support and main table in synmeans for rotating said hob support and main chronism, another table mounted on said main l0 table in synchronism first in one direction and table for rotation therewith and driven thereby, then in the opposite direction, another table means mounting said tables for relative rotative mounted on said main table for rotation theremovement therewith, and means separate from with and for relative rotation with respect thereto tool positioned to engage the sides of the hob and driven thereby, means mounting said tables teeth mounted on said another table for rotary for relative rotative movement with respectrto movementt herewith, and means separate from each other, a forming tool positioned to engage said driving means for causing said relative mOVethe sides of the hob teeth mounted on said anment by retardng and advancing the relative f0- other table for rotary movement therewith, and tative position between said tables for effecting .means for causing said relative movement by rethe relief 0n the teeth, said last-named means 20 tarding and advancing the relative rotative posiincluding means plOVlCng the driving connection tion between said tables in one direction only oi between said tables. rotation of said main table for effecting the relief 3. Apparatus fOr side-relieving the teeth of on the teeth, said last-named means including hObS having a plurality 0f Cutting teeth from one means providing the driving connection between end of the hob thread to the other, comprising, said @bien in combination, a rotatable hob support, a rotatd Apparatus for Sidoro1ieving the tooth of able, main table adapted t0 TOtate abmlt an axis hobs comprising, in combination, a rotatable hob perpendicular to the axis of rotation of said hob Support, o rotatable, moin tonie adapted to rosupport, means i0!` rotating Said hOO SUPlOOYt tate about an axis perpendicular to the axis of main table in synchronism, another table mountrotation of said non support, driving moons for ed on said main table for rotation therewith and rotating said hob support and main table in syndriven thereby, means mounting said tables for onronisms another tonie mounted on Said moin relative rotative movement with respect t0 each table for rotation therewith and for relative ro- Othel, 2 forming 5001 Positioned t0 engage the tation with respect -thereto and driven thereby, sides of the hob teeth mounted on said another means mounting said tables for relative rotative table for rotary movement therewith, and means movement with respect to oooh other, o forming causing said relative movement by retarding and tooi positioned to engage ino Sides of tno hob advancing the relative rotative position between tooth mounted on said another vaiolo for rotary said tables fOr effetng the relief Oil the teeth movement therewith, and means causing said relsaid last-named means including a rotatable cam drive movement by roi-,ordino and advancing the included in the driving Connection between Sad relative rotative position between said tables for tables, and means t0 eec' Such Tota'tll 0f the effecting the relief on the teeth, said last-named cam relative to the travel of the tool from one means including o resilient member mounted on end of the thread to the other that the relative one of said rabies, a Shiftobio @am member en rototive position between the tables is retarded gageabie with Said resilient member mounted on and advanced a' plurality 0f times in the travel the other of said tables, said last two named memflGm 0D@ end O the thread t0 the other depend bers providing the driving connection between ent upon the number 0f teeth t0 be relieved be' said tables, and means separate from said driving tween the ends of the thread for eiecting the remeans to shift said oom memberlief 011 Sad teeth 50 '7. Apparatus for side-relieving the teeth of 4 Apparatus for Side'relevng the teeth of hobs comprising, in combination, a rotatable hob hobs having a plurality of' cutting teeth from one support, a rotatable .main table adapted to rotate end of the hob thread to the other Comprising about an axis perpendicular to the axis of rotan Combination a rotatable hob Support a rotat" tion of said hob support, reversible driving means able, main table adapted to rotate about an axis for rotating Said hob Support and main ,Gable in perpendicular to the axis of rotation of said hob Synchronism mst in one direction and then* in Support means for rotating Said hob support and the opposite direction, another table mounted on mi table in Synchronsm another table tnount said main table for rotation therewith and for ed on said main table for rotation merewlth and relative rotation with respect thereto and driven driven thereby means mountmg Sad tables for thereby means mounting said tables for relative relative rotative movement with respect to each rotative movement with respect to each other, a

s'tioned to en a e the glsro trgg 132303111 lomted on Saidgaother forming tool positloned to engage the sides of the table for roi-,ar movement therewith, and moons hob teeth mounted on said another table for rocausing said rlative movement by retarding and tary movijmelt theleWlth, and msfms Callsmg advancing the relative rotative position between said Telatlve mOVement by retardlng and adsaid tables for effecting the relief en the teeth, vancins the relative rotatlve p0s1t10r1betweer1 Said said last-named means including a rotatable cam tables in one direction only of rotation of said included in the driving connection between said main table for effecting the relief 0n the teeth, tables and means to eiect such rotation of the said last-named means including a resilient memcam relative to the travel of the tool from one ber mounted on one of said tables, a shitable cam end of the thread to the other that the relative romember engageable with s aid resilient member tative position between the tables is retarded and mounted on the other of sald tables, said last two advanced a plurality of times in the travel *from named members providing the driving connection one end of the thread to the other in one direcbetween said tables, and means separate from said `11 12 driving means to shift said cam member in one Y9` Apparatus tor side-relieving .the teeth of direction only of rotation .of said main table. hobs comprising, in combnation,.a rotatable hob 8. Apparatus for side-relieving the teeth of support, a rotata le main table adapted to rotate hobs comprising, in combination, a rotatable hob about an axis perpendicular to the axis of rotasupport, a rotatable main table adapted to rotate 5 tion of said hob support, reversible driving means about an axis perpendicular to the axis of rotafor rotating said hob support and main table in tion of said hob support, reversible driving means synchronism rst in one direction and then in for rotating said hob support and main table in the opposite direction, another table mounted on synchronism rst in one direction and then in said main table for rotation therewith and for the opposite direction, another table mounted on l0 relative rotation with respect thereto and driven said main table for rotation therewith andifor relthereby, means mounting said tables for relative ative rotation with respect thereto and driven rotative movement with respect to each other,

forming tool'positioned to engage the sides of the l5 table for rotary movement therewith, and meansV hob teeth mounted on said another table for iocausing said relative movement by retarding and tary movement theiewith, and means causing advancing the relative rotative position between said relative movement by retarding and adsaid tables in one direction only of rotation of said tables in one direction only of rotation of 20 teeth, said last-named means includingamember said main table for effecting the relief on the having a cam surface mounted on one of said teeth, said last-named means incIuding a memtables, a shiftable cam member engageable with ber having a cam surface mounted on one of said said cam surface radially mounted on the other tables, a shiftable cam member engageable with of said tables, means resiliently urging said last said cam surface mounted on the other of said 25 two named members into engagement with each tables, means resiliently urging said last two other, said last two named members providing the named members into engagement with each driving connection between said tables, and means other, said last two named members providing the separate from said driving means to radially shift driving connection between said tables, and said cam member during one direction only of romeans separate from said driving means to shift 30 tation of said main table.

said cam member in a linear direction during one direction only of rotation of said main table. HARRY PELPHREY. 

